As of the 2010 United States Census, the district had a population of 217,041, of whom 162,280 were of voting age. The racial makeup of the district was 176,496 White, 3,273 African American, 216 Native American, 29,836 Asian, 49 Pacific Islander, 3,685 from some other race, and 3,486 from two or more races. Hispanic or Latino of any race were 16,408 of the population. The district had 167,330 registered voters as of February 1, 2020, of whom 71,412 were registered as unaffiliated, 48,434 were registered as Republicans, 46,260 were registered as Democrats, and 1,224 were registered to other parties. The district, which covers most of Northern Bergen County, has the smallest African-American population of any district in the state and ranks 31st in the number of Hispanic residents, while it has the ninth highest percentage of Asian residents. At 0.3% it has the lowest percentage of children receiving Temporary Assistance for Needy Families aid, just over 5% of the state average. The district ranked second-highest in both equalized property value and personal income on a per capita basis.
Throughout most of the district's history since 1973, the year the 40-district legislative map was created in New Jersey, the 39th District has encompassed the small affluent boroughs and townships in northeast Bergen County. In the redistrictings of 1981 and 1991, only a few municipalities were added and removed to get the district's population close to one fortieth of the state's population as required under the Reynolds v. Sims ruling. Changes to the district made as part of the New Jersey Legislative apportionment in 2001 removed Englewood Cliffs Borough and Tenafly Borough and Waldwick Borough and Washington Township. Changes to the district made as part of the New Jersey Legislative apportionment in 2011 removed several Bergen County municipalities and added portions of Passaic County and northwest Bergen County.
Election history
With Democrat Brendan Byrne at the top of the ticket winning the race for Governor of New Jersey, Frank Herbert won the 1977 race for Senate in the 39th District, standing together with his running mates in support of the establishment of a state income tax to defeat Republican John Markert. In the 1979 election, Gerald Cardinale and Markert defeated incumbent Democrat Greta Kiernan, who had herself defeated Markert two years earlier. Cardinale knocked off the incumbent State Senator Frank Herbert in 1981 and Herbert fell short again running against Cardinale in 1983, losing by about 1,000 votes. Citing recent hip replacement surgery as a factor, John E. Rooney announce in March 2009 that he would not seek another term of office and would retire after 26 years in the legislature. He endorsed Bob Schroeder, a Washington Township councilmember, who won election to succeed him. After Charlotte Vandervalk decided not to run for re-election in 2011, Holly Schepisi ran in her place and won together with the other Republican incumbents.
